Method for preparing InP from ITO waste

Abstract

The invention discloses a method for preparing InP from ITO waste, and belongs to the technical field of ITO waste resource recycling. The method comprises the following steps: crushing the ITO waste, and leaching indium and tin by adopting sulfuric acid to obtain an indium-tin leaching solution; phosphoric acid is added into the indium tin leaching solution for selective precipitation, and indium phosphate precipitation is obtained; carrying out reduction roasting on the indium phosphate precipitate to obtain an InP crude product; the InP crude product is subjected to sulfuric acid leaching and impurity removal, and an InP product is obtained. According to the method, a wet extraction and pyrometallurgy combined process technical means is adopted, the ITO waste can be used as a direct raw material, the high-quality InP material can be synthesized through a low-energy-consumption and simple process path, resource utilization of the ITO waste is achieved, and the production cost of InP is reduced.

Description

Technical Field

[0001] The present invention relates to a method for recycling ITO waste, in particular to a method for preparing InP from ITO waste, and belongs to the technical field of resource utilization of ITO waste. Background Art

[0002] ITO waste is a high-risk solid waste generated in the manufacturing process of the optoelectronic display industry, which is generated in the processing, use and recycling links of indium tin oxide (ITO) targets. Waste targets are the leftover scraps or defective products remaining after the ITO targets are used in magnetron sputtering coating. With the rapid development of the global display panel, touch screen and photovoltaic industries, the demand for ITO targets has increased sharply, and the output of waste targets has also risen accordingly. However, the existing technologies for recycling waste targets have high technical thresholds and high treatment costs, and their comprehensive recovery rates are very low. A large amount of waste targets are sealed or landfilled for a long time, resulting in increasingly serious problems of resource waste and environmental pollution. The indium content in ITO waste can reach 80% - 90%, which is much higher than that of primary indium ore. The indium value per ton of ITO waste is as high as one million yuan, with extremely high recycling economic value.

[0003] In the field of semiconductor materials, indium phosphide (InP) has become the core material for high-frequency devices due to its excellent electron mobility and optoelectronic properties. However, the traditional high-temperature synthesis method has high raw material costs and high energy consumption, which seriously restricts the development of the industry. For example, Chinese Patent (Publication No. CN111472047B) discloses an indium phosphide crystal and its growth method. In this method, indium blocks and phosphorus grains are placed in an atmospheric pressure polycrystalline synthesis furnace. First, the temperature is raised to melt the indium. After the phosphorus grains are completely absorbed by the molten indium, the temperature is gradually raised to 1030 - 1100 °C to obtain indium phosphide polycrystals.

[0004] Based on the technical defects existing in the existing indium phosphide preparation process, if the by-product ITO waste in the flat panel display industry can be resourcefully utilized to prepare high-value-added InP materials through a simple metallurgical process, the production cost of indium phosphide will be greatly reduced, and it will have broad application prospects. Summary of the Invention

[0005] Aiming at the technical problems existing in the existing resource utilization of ITO waste and the indium phosphide preparation process, the purpose of the present invention is to provide a method for preparing InP from ITO waste. This method adopts the combined process technology of wet extraction and pyrometallurgy, and can use ITO waste as the direct raw material to synthesize high-quality InP materials through low energy consumption and a simple process path, realizing the resource utilization of ITO waste and reducing the production cost of InP.

[0006] In order to achieve the above technical objectives, the present invention provides a method for preparing InP from ITO waste. The method involves crushing the ITO waste and then leaching indium and tin with sulfuric acid to obtain an indium-tin leaching solution; adding phosphoric acid to the indium-tin leaching solution for selective precipitation to obtain indium phosphate precipitation; subjecting the indium phosphate precipitation to reduction roasting to obtain a crude InP product; and subjecting the crude InP product to sulfuric acid leaching for impurity removal to obtain an InP product.

[0007] The key to the technical solution of the present invention lies in: First, selectively extract tin and indium, and make full use of the solubility difference between indium tin oxide and impurity components in sulfuric acid to achieve the selective extraction of indium and tin, and preliminarily remove most impurities; Second, separate tin and indium through phosphorylation, and make full use of the difference in solubility products of indium phosphate and tin phosphate to achieve the separation of indium and tin; Third, achieve the obtaining of indium phosphide at low temperature through the reduction conversion of indium phosphate, and use a weakly reducing atmosphere to directionally reduce indium phosphate to InP; Finally, use sulfuric acid leaching for deep impurity removal, relying on the solubility difference between indium phosphate and InP in sulfuric acid at high temperature to achieve the purification of the InP product, and finally obtain an InP product with a purity of more than 99.9%.

[0008] As a preferred solution, the particle size of the crushed ITO waste satisfies that the mass ratio less than 0.074 mm is greater than 80%. The ITO waste of the present invention is the waste generated during the ITO sputtering production process. The ITO waste is crushed to be sufficiently fine to enable the full monomer dissociation of each phase in the ITO waste, ensuring good subsequent leaching and impurity removal effects.

[0009] As a preferred solution, the conditions for leaching indium and tin with sulfuric acid are as follows: the concentration of H 2 SO 4 is 80 - 120 g / L, the liquid-solid ratio is 9 - 11 mL / g, the leaching time is 2 - 3 hours, and the leaching temperature is 80 - 120 °C. During the process of leaching indium and tin with sulfuric acid, the leaching efficiency and leaching selectivity of indium and tin are mainly affected by the concentration of H 2 SO 4 and the temperature. For example, the lower the concentration of H 2 SO 4 and the lower the leaching temperature, the lower the leaching efficiency of indium and tin, while the higher the concentration of H 2 SO 4 and the higher the leaching temperature, although the leaching efficiency of indium and tin is higher, it will also lead to an increase in the leaching rate of other impurities. The liquid-solid ratio of the leaching solution and the leaching time are secondary factors affecting the leaching efficiency and leaching selectivity of indium and tin. For example, when other conditions are certain, the effect on the leaching rate is very small when the liquid-solid ratio is greater than 9 mL / g, and too high a liquid-solid ratio leads to difficulties in subsequent precipitation and waste of acid solution. After other conditions are optimized, an indium leaching rate of more than 99% can be achieved after leaching for more than 2 hours. When the temperature is low or the concentration of H2 SO 4 When the concentration is low, the leaching time needs to be appropriately extended.

[0010] As a preferred solution, during the selective precipitation process, phosphoric acid is added and the pH is controlled within the range of 6.2 - 6.5. Within the range of 6.2 - 6.5, it belongs to the optimal precipitation pH range of indium phosphate to reduce the impurity content in indium phosphate.

[0011] As a preferred solution, the conditions for the reduction roasting are as follows: in an atmosphere containing hydrogen, at a temperature of 550 - 700 °C, roasting for 45 - 90 min. The temperature of the reduction roasting depends on the temperature at which indium phosphate is reduced by hydrogen. When the temperature is too low, the reaction is difficult to occur or the rate is very low even if it occurs. After exceeding the temperature limit, a higher temperature does not bring a significant increase in the reaction rate but will instead consume a large amount of energy additionally.

[0012] As a preferred solution, the hydrogen-containing atmosphere includes H 2 and H 2 O mixed gas, and the volume ratio of H 2 / H 2 O is 4 - 20. The partial pressure of H 2 in the hydrogen-containing atmosphere needs to be controlled within an appropriate range. When the partial pressure of H 2 is on the low side, the Gibbs free energy of the reduction reaction is still relatively high and the reaction rate is low. When the partial pressure of H 2 is on the high side, too high a partial pressure of the reducing gas is likely to cause indium phosphate to be over-reduced to metallic indium. The hydrogen-containing atmosphere is maintained by continuously introducing H 2 and H 2 O mixed gas. The flow rate of the H 2 and H 2 O mixed gas is 0.05 - 0.1 L / min (relative to each gram of indium phosphate raw material). If the gas flow rate is too small, it will lead to insufficient supply of the reducing gas. After the flow rate exceeds a certain limit, it will no longer have a positive impact on the reaction and will cause waste of resources.

[0013] As a preferred solution, the conditions for the sulfuric acid leaching and impurity removal are as follows: the concentration of H 2 SO 4 is 80 - 120 g / L, the temperature is 120 - 150 °C, and the leaching time is 6 - 9 hours. Under the preferred conditions, it is possible to utilize the solubility difference between indium phosphate and InP in sulfuric acid to remove a small amount of incompletely converted indium phosphate in the InP product, and finally obtain an InP product with a purity of more than 99.9%. At an appropriate sulfuric acid concentration, increasing the temperature can increase the solubility of indium phosphate, while indium phosphide is not affected. Therefore, the two are separated by using the solubility difference between them.

[0014] Advantageous technical effects brought by the technical solution of the present invention compared with the prior art:

[0015] 1) The present invention proposes a method for preparing InP materials from ITO waste, adopting the technical means of combining hydrometallurgy and pyrometallurgy, enabling the resource recycling of ITO waste as solid waste, and obtaining high-quality InP materials at the same time, providing a new path for the comprehensive utilization of ITO waste and the production of InP, and solving the technical problems such as the difficult recycling of current ITO waste and the high production cost of indium phosphide.

[0016] 2) The present invention can use large-scale industrial mature equipment such as existing rotary kilns and reduction shaft furnaces for production, with a simple technical route, greatly improving production efficiency and resource utilization rate. The solutions and gases used are common and frequently used in industrial production processes, which is conducive to realizing large-scale and industrialization.

[0017] 3) In the process of preparing InP materials from ITO waste, the present invention makes full use of the solubility differences of indium tin oxide and impurity components in sulfuric acid to achieve selective extraction of indium and tin, and then realizes the separation of indium and tin through the solubility product differences of indium phosphate and tin phosphate. Then, using a weak reducing atmosphere of H 2 phosphate indium is directionally reduced to InP, and finally, the product is purified by virtue of the solubility differences of indium phosphate and InP in sulfuric acid at high temperature, obtaining high-value-added InP products while realizing the resource recovery of ITO waste. Detailed implementation manners

[0018] The following examples are intended to further illustrate the content of the present invention rather than limit the protection scope of the claims of the present invention.

[0019] Comparative example 1

[0020] This comparative example is used to illustrate that if the crushing fineness of the raw material is insufficient, it is not conducive to leaching and reduction.

[0021] Compared with Example 1, the only difference is that the ITO waste is finely crushed to a proportion of 30% with a particle size of -0.074 mm.

[0022] The performance of the obtained product was detected: the purity of InP was only 97.2%, and the indium recovery rate was only 56.8%.

[0023] Comparative example 2

[0024] This comparative example is used to illustrate that if the leaching acidity is too low, it is not conducive to leaching and impurity removal.

[0025] Compared with Example 1, the only difference is that the ITO waste finely crushed to a proportion of 80% with a particle size of -0.074 mm is used with 50 g / L of H 2 SO 4Leaching was carried out with a liquid-solid ratio of 11 mL / g, a leaching time of 2 hours, and a leaching temperature of 120 °C.

[0026] The obtained product was subjected to performance testing: the purity of InP was only 97.8%, and the indium recovery rate was only 47.2%.

[0027] Comparative Example 3

[0028] This comparative example is used to illustrate that if the leaching temperature is low, it is not conducive to leaching and impurity removal.

[0029] Compared with Example 2, the only difference is that ITO waste crushed to 90% with a particle size of -0.074 mm was leached with H 2 SO 4 Leaching was carried out with a liquid-solid ratio of 9 mL / g, a leaching time of 3 hours, and a leaching temperature of 60 °C.

[0030] The obtained product was subjected to performance testing: the purity of InP was only 96.7%, and the indium recovery rate was only 42.9%.

[0031] Comparative Example 4

[0032] This comparative example is used to illustrate that if the pH is too low during phosphoric acid precipitation, it is difficult to form indium phosphate precipitation.

[0033] Compared with Example 2, the only difference is that phosphoric acid was added to the obtained leaching solution and the pH was adjusted to 4.0 to obtain a precipitate.

[0034] The obtained product was subjected to performance testing: the purity of InP was 99.9%, and the indium recovery rate was only 8.9%.

[0035] Comparative Example 5

[0036] This comparative example is used to illustrate that if the hydrogen concentration is insufficient, it is not conducive to the reduction of indium phosphate to indium phosphide.

[0037] Compared with Example 3, the only difference is that the precipitate was subjected to reduction roasting, and the H 2 / HO volume ratio was 2, the flow rate was 0.1 L·min 2 -1 per g of raw material, the roasting temperature was 550 °C, and the heat preservation time was 90 minutes.

[0038] The obtained product was subjected to performance testing: the purity of InP was only 78.2%, and the indium recovery rate was 46.8%.

[0039] Comparative Example 6

[0040] This comparative example is used to illustrate that if the roasting temperature is low, it is not conducive to the reduction of indium phosphate to indium phosphide.

[0041] Compared with Example 3, the only difference is that the precipitate is subjected to reduction roasting, with the H 2 / H 2 O volume ratio being 4 and the flow rate being 0.1 L·min -1 per gram of raw material, the roasting temperature is 400 °C, and the heat preservation is for 90 minutes.

[0042] Performance testing was carried out on the obtained product: the purity of InP was only 72.7%, and the indium recovery rate was 33.5%.

[0043] Comparative Example 7

[0044] This comparative example is used to illustrate that if the temperature is too low during high-temperature leaching for impurity removal, it is difficult to remove indium phosphate impurities.

[0045] Compared with Example 4, the only difference is that the roasted product is further leached with 80 g / L of H 2 SO 4 at 100 °C for 9 hours, and the high-temperature leaching residue is the InP precursor material.

[0046] Performance testing was carried out on the obtained product: the purity of InP was only 87.9%, and the indium recovery rate was only 56.8%.

[0047] Example 1

[0048] Using the ITO waste from a certain factory (the indium-tin ratio In 2 O 3 / SnO 2 = 9, the Al 2 O 3 content is 0.4%, the TiO 2 content is 0.3%, and it also contains trace amounts of impurities such as Fe, Zr, W, and Cu), sulfuric acid, phosphoric acid, and hydrogen as raw materials. First, the ITO waste that has been crushed to -0.074 mm with a proportion of 80% is leached with 80 g / L of H 2 SO 4 , the liquid-solid ratio is 11 mL / g, the leaching time is 2 hours, and the leaching temperature is 120 °C; phosphoric acid is added to the obtained leaching solution and the pH is adjusted to 6.2 to obtain a precipitate, and the precipitate is subjected to reduction roasting, with the H 2 / H 2 O volume ratio being 4 and the flow rate being 0.05 L·min -1 per gram of raw material, the roasting temperature is 550 °C, and the heat preservation is for 90 minutes; the roasted product is further leached with 80 g / L of H 2 SO 4 at 120 °C for 9 hours, and the high-temperature leaching residue is the high-quality InP precursor material.

[0049] Performance testing was carried out on the obtained product: the purity of InP was 99.9%, and the indium recovery rate was 90.8%.

[0050] Example 2

[0051] Using the ITO waste from a certain factory (In / SnO ratio is 9, Al content is 0.4%, TiO content is 0.3%, and it also contains trace impurities such as Fe, Zr, W, Cu, etc.), sulfuric acid, phosphoric acid, and hydrogen as raw materials. First, the ITO waste that has been finely crushed to a ratio of 90% with a particle size of -0.074 mm is leached using 120 g / L of H 2 O 3 / SnO 2 =9, Al 2 O 3 content of 0.4%, TiO 2 content of 0.3%, and also contains trace impurities such as Fe, Zr, W, Cu, etc.), sulfuric acid, phosphoric acid, and hydrogen as raw materials. First, the ITO waste that has been finely crushed to a ratio of 90% with a particle size of -0.074 mm is leached using 120 g / L of H 2 SO 4 at a liquid-solid ratio of 9 mL / g and a leaching time of 3 hours at a leaching temperature of 120°C; the obtained leachate is added with phosphoric acid and the pH is adjusted to 6.2 to obtain a precipitate, and the precipitate is subjected to reduction roasting, with the H 2 / H 2 O volume ratio of 4 and a flow rate of 0.05 L·min -1 per g of raw material, a roasting temperature of 550°C, and a holding time of 90 minutes; the roasted product is then leached at 120°C using 80 g / L of H 2 SO 4 for 9 hours, and the high-temperature leaching residue is the high-quality InP precursor material.

[0052] The performance of the obtained product is tested: the purity of InP is 99.9%, and the indium recovery rate is 91.2%.

[0053] Example 3

[0054] Using the ITO waste from a certain factory (In / SnO ratio is 9, Al content is 0.4%, TiO content is 0.3%, and it also contains trace impurities such as Fe, Zr, W, Cu, etc.), sulfuric acid, phosphoric acid, and hydrogen as raw materials. First, the ITO waste that has been finely crushed to a ratio of 80% with a particle size of -0.074 mm is leached using 80 g / L of H 2 O 3 / SnO 2 =9, Al 2 O 3 content of 0.4%, TiO 2 content of 0.3%, and also contains trace impurities such as Fe, Zr, W, Cu, etc.), sulfuric acid, phosphoric acid, and hydrogen as raw materials. First, the ITO waste that has been finely crushed to a ratio of 80% with a particle size of -0.074 mm is leached using 80 g / L of H 2 SO 4 at a liquid-solid ratio of 11 mL / g and a leaching time of 2 hours at a leaching temperature of 80°C; the obtained leachate is added with phosphoric acid and the pH is adjusted to 6.5 to obtain a precipitate, and the precipitate is subjected to reduction roasting, with the H 2 / H 2 O volume ratio of 4 and a flow rate of 0.1 L·min -1 per g of raw material, a roasting temperature of 550°C, and a holding time of 90 minutes; the roasted product is then leached at 120°C using 80 g / L of H 2 SO 4Leach at 120 °C for 9 hours, and the high-temperature leaching residue is the high-quality InP precursor material.

[0055] Perform performance testing on the obtained product: InP purity is 99.9%, and indium recovery rate is 92.1%.

[0056] Example 4

[0057] Using the ITO waste from a certain factory (indium-tin ratio In 2 O 3 / SnO 2 = 9, Al 2 O 3 content is 0.4%, TiO 2 content is 0.3%, and containing trace impurities such as Fe, Zr, W, Cu, etc.), sulfuric acid, phosphoric acid, and hydrogen as raw materials. First, leach the ITO waste with a particle size of -0.074 mm accounting for 80% using 80 g / L of H 2 SO 4 leach, the liquid-solid ratio is 11 mL / g, the leaching time is 2 hours, and the leaching temperature is 120 °C; add phosphoric acid to the obtained leaching solution and adjust the pH to 6.2 to obtain a precipitate, and perform reduction roasting on the precipitate, H 2 / H 2 O volume ratio is 20, the flow rate is 0.05 L·min -1 per g of raw material, the roasting temperature is 700 °C, and keep warm for 45 minutes; the roasted product is then leached with 80 g / L of H 2 SO 4 Leach at 120 °C for 9 hours, and the high-temperature leaching residue is the high-quality InP precursor material.

[0058] Perform performance testing on the obtained product: InP purity is 99.9%, and indium recovery rate is 90.2%.

[0059] Example 5

[0060] Using the ITO waste from a certain factory (indium-tin ratio In 2 O 3 / SnO 2 = 9, Al 2 O 3 content is 0.4%, TiO 2 content is 0.3%, and containing trace impurities such as Fe, Zr, W, Cu, etc.), sulfuric acid, phosphoric acid, and hydrogen as raw materials. First, leach the ITO waste with a particle size of -0.074 mm accounting for 80% using 80 g / L of H 2 SO 4 leach, the liquid-solid ratio is 11 mL / g, the leaching time is 2 hours, and the leaching temperature is 120 °C; add phosphoric acid to the obtained leaching solution and adjust the pH to 6.2 to obtain a precipitate, and perform reduction roasting on the precipitate, H 2 / H2 The volume ratio of O is 4 and the flow rate is 0.05 L·min -1 For every gram of raw material, the roasting temperature is 550 °C and the heat preservation time is 90 minutes; the roasted product is then treated with H at 120 g / L 2 SO 4 Leach at 150 °C for 6 hours, and the high-temperature leaching residue is the high-quality InP precursor material.

[0061] Perform performance testing on the obtained product: the purity of InP is 99.9% and the indium recovery rate is 91.5%.

Claims

1. A method for preparing InP from ITO waste, characterized in that: After the ITO waste is crushed, indium and tin are leached with sulfuric acid to obtain an indium-tin leaching solution; phosphoric acid is added to the indium-tin leaching solution for selective precipitation to obtain an indium phosphate precipitate; the indium phosphate precipitate is subjected to reduction roasting to obtain an InP crude product; the InP crude product is leached with sulfuric acid to remove impurities to obtain an InP product.

2. The method for preparing InP from ITO waste according to claim 1, characterized in that: The mass proportion of the ITO waste crushed to a particle size less than 0.074 mm is greater than 80%.

3. The method for preparing InP from ITO waste according to claim 1 or 2, characterized in that: The conditions for leaching indium and tin with sulfuric acid are: H2SO4 concentration is 80-120 g / L, liquid-to-solid ratio is 9-11 mL / g, leaching time is 2-3 hours, and leaching temperature is 80-120°C.

4. The method for preparing InP from ITO waste according to claim 1, characterized in that: During the selective precipitation process, phosphoric acid is added and the pH is controlled within the range of 6.2 to 6.

5.

5. The method for preparing InP from ITO waste according to claim 1, characterized in that: The reduction roasting conditions are: roasting at a temperature of 550-700° C. for 45-90 minutes in a hydrogen-containing atmosphere.

6. The method for preparing InP from ITO waste according to claim 5, characterized in that: The hydrogen-containing atmosphere includes a mixed gas of H2 and H2O, and the volume ratio of H2 / H2O is 4-20.

7. The method for preparing InP from ITO waste according to claim 1 or 5, characterized in that: The conditions for sulfuric acid leaching and impurity removal are: H2SO4 concentration is 80-120 g / L, temperature is 120-150°C, and leaching time is 6-9 hours.